The present invention relates to apparatus for supporting a moving material web, and more particularly to a rotating reel for engagement with an advancing material web.
In the handing of a packing material web which is provided with a regular pattern of transverse crease lines, the crease line pattern is frequently used for checking and adjusting the registry of the web during the feed so that any processing operations can take place in register with the crease line pattern. This registry may be achieved with the help of different types of registry devices, such as by means of a rotating reel. The reel usually comprises several rules, which are parallel with the axis of rotation of the reel, each being provided with an edge for engagement with transverse crease lines of the web. The reel may drive the web or be driven by the same and it may be made use of for the control of other operations, including printing or driving of the web.
To ensure that the reel maintains its engagement in register with the crease lines, the edges of the rules are ground to be relatively sharp. This functions well on packing material webs of the type where the transverse crease lines co-operating with the reel extend over the whole width of the material. In the case of shorter crease lines which extend only over a limited part of the web width, the edges of the rules must be made shorter so that they do not run out , over, and fold, the material web also in the areas where these crease lines are lacking. These non-creased areas of the material web are usually located along the longitudinal edges of the material web where a sealing process frequently has to be carried out as the material web is being converted to packing containers. This makes it particularly important that these edge areas should be non-folded and plane so as to ensure that the sealing produces a completely liquid-tight join. In case of shorter creases, that is to say creases which extend over a part of the width of the material web, it is thus necessary to provide the reel with shorter rules. It has been found that whilst folding damage in the non-creased areas is prevented by this measure, damage is quite likely to occur on the other hand at the points where the rules or edges terminate. Such damage frequently arises in particular where the web is stressed, that is to say where it is pressed relatively strongly against the edges of the rules which, however, is often necessary so as to ensure registry and to prevent the edges of the reel from ending up outside the crease lines. The problem is particularly great where material webs are processed whereon the mutual distance between the transverse crease lines does not exactly correspond to the specified distance which, of course, has also been chosen as the distance between the edges of the rules on the reel as measured (along the circumference of the reel). This happens relatively often, since the tolerances relating to the distance between the crease lines have to be kept relatively large for reasons connected with the methods of manufacture.